Confinement – assisted shock-wave-induced thin-film delamination (SWIFD) of copper indium gallium diselenide (CIGS) on a flexible substrate

Highlights: • The shock-wave-induced thin-film delamination (SWIFD) process was studied. • At SWIFD a rear side irradiation induced a shockwave which induced a delamination. • The SWIFD process allows the non-thermal structuring of CIGS solar cell material. • The process is dependent on the laser parameter and on the confinement conditions. - Abstract: The laser structuring of CIGS (copper indium gallium (di)selenide) solar cell material without influence and damaging the functionality of the active layer is a challenge for laser methods The shock-wave-induced thin-film delamination (SWIFD) process allows structuring without thermal modifications due to a spatial separation of the laser absorption from the functional layer removal process. In the present study, SWIFD structuring of CIGS solar cell stacks was investigated. The rear side of the polyimide was irradiated with a KrF-Excimer laser. The laser-induced ablation process generates a traverse shock wave, and the interaction of the shock wave with the layer-substrate interface results in a delamination process. The effect of a water confinement on the SWIFD process was studied where the rear side of the substrate was covered with a ∼2 mm thick water layer. The resultant surface morphology was analysed and discussed. At a sufficient number of laser pulses N and laser fluences Φ, the CIGS layer can be selectively removed from the Mo back contact. The water confinement, as well as the increasing laser beam size A₀ and N, results in the reduction of the necessary minimal laser fluence Φ_th. Further, the delaminated CIGS area increased with increasing Φ, N, and A₀.